A friend of mine , who is a software professional called from Germany to ask me if she could fly during pregnancy as she was concerned about radiation. A GP colleague asked whether MRI for his patient was safe. I thought it was a good idea to refresh myself with what is the latest information available on these.
Coming to the safety of radiation in pregnancy, the main questions for a Clinician are
(a) Question of necessity of investigation &
(b) Fetal effects of the investigation done.
'Is it safe, doctor?' is a common question we would face!
'Is it safe, doctor?' is a common question we would face!
With regards to Question of necessity, If an intervention to save the mother or fetus could be made, by doing an MRI or X-ray or IVU, then it needs to be done, where benefits of saving the mother would outweigh the risks.
About the Fetal effects, the safety of imaging would be questioned by patients particularly, if the fetus is in embryonic stage or in first trimester. Clinicians aoften face the situation to explain if it is essential and what harm it could do to the fetus.
The risk of central nervous system effects is greatest with exposure at 8–15 weeks of gestation, with no proven risk at less than 8 weeks of gestation or at greater than 25 weeks of gestation. Thus, at 8–15 weeks of gestation, the foetus is at greatest risk for radiation-induced mental retardation, and the risk appears to be a "no threshold linear function of dose" at doses of at least 20 rad.
It is important to understand what rad is to gray. The following is commonly used.
· 1 rad = 0.01 Gy = 1 rem
· 1 mrad = 0.01 mGy
Xray : Women should be counselled that X-ray exposure from a single diagnostic procedure does not result in harmful foetal effects. Specifically, exposure to less than 5 rad has not been associated with an increase in foetal anomalies or pregnancy loss.
The estiamted exposure for common procedures are as follows:
chest Xray has 0.02 mrad ,
CT head has < 1 rad and
Mammography has <20 mrad.
IVU has > 1 rad and CT abdomena dn lumbar spine has 3.5 rad.
Ultrasound : safe in pregnancy.
MRI is considered safer in pregnancy than CT imaging. The two important effects concerned theoretically, would be teratogenicity and acoustic damage to fetus due to MRI.
Although, No damage to the developing human fetus caused by MRI has been documented, all guidelines seem to say that caution is advised, and risks and benefits must always be considered before evaluating a pregnant patient with MR imaging.
The 2009 Health Protection Agency, Royal College of Radiologists and College of Radiographers (RCR) echo the same as the 2007 Medicines and Healthcare products Regulatory Agency (MHRA). Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use.
"The MHRA recommends that, where possible, the decision to scan
should be made at the time by the referring clinician, an MR radiologist and the patient, based on the information above about risks weighed against the clinical benefit to the patient."
Although, No damage to the developing human fetus caused by MRI has been documented, all guidelines seem to say that caution is advised, and risks and benefits must always be considered before evaluating a pregnant patient with MR imaging.
The 2009 Health Protection Agency, Royal College of Radiologists and College of Radiographers (RCR) echo the same as the 2007 Medicines and Healthcare products Regulatory Agency (MHRA). Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use.
"The MHRA recommends that, where possible, the decision to scan
should be made at the time by the referring clinician, an MR radiologist and the patient, based on the information above about risks weighed against the clinical benefit to the patient."
With regards to radiation exposure with flying during pregnancy,
The Airport Security Scanners & Ionising Radiation, a working group of The Royal College of radiologists (RCR) and British Institute of Radiology (BIR) have released a report in 2011 stating that ‘Airport body scanners are safe’. The average dose form a single scan is 100000 times lower than the average annual dose of radiation a person receives from natural background radiation and medical resources.
HPS, a society for Radiation safety states that the radiation exposures while flying are not considered high exposures. For example, in a 10-hour flight, the exposure would be less than 1 milliard, which would bring the exposure in the range of a low-level exposure from many diagnostic radiological procedures. This exposure would not increase the risk for birth defects or miscarriage.
So, a summary of most guidelines would be the following:
1. The standard dose of radiation associated with a diagnostic x-ray produces a minuscule risk to the foetus. However, all women of childbearing age are asked if they are pregnant before any exposure to radiation.
2. Concern about possible effects of high-dose ionizing radiation exposure should not prevent medically indicated diagnostic X-ray procedures from being performed on a pregnant woman.
3. During pregnancy, other imaging procedures not associated with ionizing radiation (e.g., ultrasonography, MRI) should be considered instead of X-rays when appropriate. Ultrasonography and MRI are not associated with known adverse foetal effects.
4. The use of radioactive isotopes of iodine is contraindicated for therapeutic use during pregnancy.
5. Radiopaque and paramagnetic contrast agents are unlikely to cause harm and may be of diagnostic benefit, but these agents should be used during pregnancy only if the potential benefit justifies the potential risk to the foetus.
6. Airport scanners are safe and have miniscule radiation exposure,
7. During pregnancy, a woman and her foetus will receive about 300 milliard of background radiation (which of course no-one can avoid). The background risk is 3% for birth defects and 15% for miscarriage for all healthy women when they begin their pregnancy. This is not increased due to flying during pregnancy.
Useful information can be found on these links:
